RT Journal Article SR Electronic T1 Different seasons with decreased performance of immunochemical faecal occult blood tests in colorectal cancer screening JF Gut JO Gut FD BMJ Publishing Group Ltd and British Society of Gastroenterology SP 1303 OP 1304 DO 10.1136/gut.2010.223412 VO 60 IS 9 A1 Leo G M van Rossum A1 Martijn G H van Oijen YR 2011 UL http://gut.bmj.com/content/60/9/1303.2.abstract AB